1. Field of the Invention
The present invention generally relates to a back light module of a liquid crystal display, and more particularly to a back light module of a liquid crystal display (LCD) having a housing which can be easily detached.
2. Description of the Related Art
Due to the advance of electronic technology, especially for the popularity of portable electronic products, the requirements of light, compact and low-energy consuming display are gradually increasing. With the advantages of low-energy consuming, low-heat dissipation, light weight and non-luminescence display, liquid crystal displays (LCD) have been widely used in the electronic products and even have replaced the traditional CRT displays.
Referring to FIG. 1, it depicts a conventional liquid crystal display (LCD). In general, the liquid crystal display includes a liquid crystal panel 10 which has two substrates and liquid crystal material sealed therebetween, a back light module 20 disposed under the liquid crystal display panel 10, and a front frame 11.
The back light module 20 is used to distribute the light transmitted from a light source uniformly over the surface of the liquid crystal display panel 10. There are several kinds of back light modules for the liquid crystal display, such as a direct back light type (or direct type) and an edge light type. For the liquid crystal display in large dimensions, the back light module of the direct type is widely used because of its easy installation and its low cost.
The back light module 20 of the direct type, as shown in FIG. 2, includes a housing 70 which has a reflective sheet 60 disposed on the bottom surface of the housing 70, lamps 50, such as a fluorescence cathode tube, disposed at the bottom portion of the housing 70, a diffuser plate 40 disposed on the upper surface of the housing 70, and a plurality of optical films 30, such as a prism sheet and a diffuser sheet, disposed on the diffuser plate 40. The lamps 50 are spaced apart from each other and disposed within the display area of the liquid crystal panel 10, not shown. Since the light source, i.e. the lamps 50, is a linear light source, the lamps 50 cannot provide light evenly illuminating the liquid crystal panel 10. Therefore, the diffuser plate 40 and the optical films 30 have to be provided and disposed between the lamps 50 and the liquid crystal panel 10 so as to form a panel light source device having uniform luminance.
Many back light modules have been disclosed in the prior art, such as those disclosed in U.S. Pat. No. 6,407,781 B2 issued to Kitada on Jun. 18, 2002 and in U.S. Pat. No. 6,417,833 B1 issued to Takemoto et al. on Jul. 9, 2002, which are all incorporated herein by reference.
For the well-known technology, the lifetime of the lamp of the back light module is the shortest of all the parts or elements of the liquid crystal display. If the lamp malfunctions, the frame, the liquid crystal panel, the back light module frame, the optical film, and the diffusing sheet of the liquid crystal display have to be detached from the liquid crystal display to replace the lamp. This procedure, which is difficult and complex, must be carried out in the cleaning room, or the liquid crystal panel or the optical film will be contaminated and the liquid crystal display will be degraded. Further, the liquid crystal display in large dimensions will be unable to be serviced on site without the cleaning room.
Accordingly, there exists a need for a liquid crystal display having detachable lamps for facilitating the service and the repair.